The Queries by Node plot shows the
amount of queries coming from each node in the server
cluster. If you would like to see the traffic for
a single node, select the node name in the Servers/Nodes
menu on the left.

Note that the By Node option disappears from the
Plots list when you are viewing the data for a single node.
It reappears if you click on the Server name in the
Servers/Nodes menu.